Research On Resource Allocation Optimization For The Cooperative Non-orthogonal Multiple Access

The recent progress of Mobile Internet(MI)and Internet of Things(IoT)have led to an exponential rapid growth in the number of terminals in the future.It poses new challenges to the number of wireless network connections and spectrum efficiency.In order to effectively improve the overall frequency efficiency of the system and support a large number of users to access the network,Non-Orthogonal Multiple Access(NOMA)technology appears.NOMA is considered to be one of the most promising technologies in the future fifth-generation mobile communication system(5G).Its distinctive feature is that it allows multiple users to share communication resources on the same frequency and at the same time,and user identification and differentiation through user power differences.Therefore,NOMA has a higher spectrum efficiency and the technical advantages of supporting larger-scale user connections.In NOMA,due to the introduction of Successive Interference Cancellation(SIC),strong channel users will inevitably obtain the transmission information of weak channel users during the decoding process.And the spatial diversity introduced by this decoding structure feature can be fully utilized through cooperative communication,improving the performance of weak channel users.In cooperative NOMA,the optimal allocation of resources and the selection of cooperative users are the key to achieving a compromise between system performance and complexity.Therefore,it is of great significance to study the resource allocation and relay selection strategies in cooperative NOMA.This paper takes cooperative NOMA as the object,and aims to improve the overall throughput and overall spectrum efficiency of the system,and studies the resource allocation of cooperative NOMA in different scenarios.Using tools such as game theory and convex optimization theory,this paper has designed resource allocation optimization schemes for different performance requirements.Firstly,in the NOMA cooperative spectrum resource sharing system,power allocation and relay selection strategies based on the Nash bargaining theory is proposed.This technique maximizes the product of utility functions of users participating in the cooperation and the total rate.Furthermore,the traditional mobile edge computing(MEC)communication system introduces NOMA and cooperative relay communication technology,and proposes a joint optimization technology of transmission time and transmit power in NOMA cooperative relay communication based on MEC.This technology can minimize the total energy consumption of the system.The main contributions of this paper are as follows:1)In order to meet the different needs of multiple users communicating at the same time,this paper introduces NOMA to the cooperative spectrum resource sharing system,and the introduction of relay communication technology also expands the communication range of the original system.In this NOMA cooperative spectrum resource sharing system model,in order to improve the overall rate of the system,two power allocation and relay selection strategies based on the Nash bargaining theory is proposed.First,a typical downlink communication scenario is considered.Based on this,the rate obtained by cooperative communication between each primary user(PU)and secondary user(SU)is derived and the corresponding utility function is constructed.Then,the cooperation relationship between the primary user and the secondary user is modeled as a multiple user Nash bargaining theoretical model,and an optimization problem is proposed.The goal of the optimization problem is to maximize the product of the utility functions of the PU-SU pair.Then,for the optimization problem,an ideal power allocation scheme and relay selection strategy are proposed.Finally,simulation results show that the proposed power allocation scheme and relay selection strategy can significantly improve the rate of each user of the system.2)The paper introduces the NOMA cooperative relay technology into the traditional MEC communication system,thereby effectively solving the problem of insufficient communication resources in the existing MEC system and reducing system energy consumption.Firstly,in the NOMA cooperative relay uplink communication system based on MEC,the rate of each user is calculated,and then the energy consumption of each transmission phase and the local calculation part is studied.Then,with the goal of minimizing the total energy consumption of the system,an optimization problem is proposed,and the transmission time and transmission power are jointly optimized.Based on the above optimization problem,and using related knowledge of convex optimization theory,the Lagrangian dual method is used to obtain the optimal solution of the optimization problem.Finally,simulation results show that the proposed joint optimization technology can effectively reduce the total energy consumption of the system.